1. Statement of the Technical Field
The inventive arrangements relate to methods for determining the location of lightning strikes, and more particularly, methods for locating such lightning strikes using time difference of arrival techniques.
2. Description of the Related Art
A variety of systems and methods have been developed for identifying the occurrence and location of lightning strikes, such as ground strokes. Most such systems identify the occurrence of lighting based on characteristic electromagnetic energy patterns that are associated with lightning strikes.
Several different methods can be used for determining the location of lightning strikes. One such method employs a time-difference-of-arrival (TDOA) discrimination scheme. Systems using this method typically include three or four monitoring stations that are geographically separated by some distance. Each station includes a lightning stroke detector and a timing signal generator that is synchronized with the timing signal generator at each other respective detection location. When a lightning stroke occurs, the time of detection of the ground stroke is recorded at each station. This timing information is communicated from each of the monitoring stations to a central processing station. By using timing data from each monitoring station, the location of the lighting stroke can easily be determined. For example, in the case where four monitoring stations are used, an algorithm for determining the location of the ground stroke is fairly simple, being reduced to the solution of a set of linear equations.
In general, the accuracy and resolution of TDOA type location systems are traded off to reduce the amount of data passed over the communication link. For example, a high degree of accuracy could be obtained if electromagnetic waveforms were demodulated at the remote monitoring stations, and the entire digitized signal was forwarded to a central processor system to compute the time of arrival (TOA) for each monitoring station. A generalized cross-correlation method can be used at the central processor to compute the TDOA values associated with each monitoring station. Still, there are drawbacks to such an approach. The accuracy of a TDOA estimate in such a system would be completely determined by the effective signal-to-noise ratio (SNR), signal time duration, and signal bandwidth. Thus, large amounts of bandwidth are required for transmission of data to fully represent the entire digitized signal from the monitoring station, to the central processor.
From the foregoing, it will be appreciated that the tradeoff between accuracy and communication link bandwidth is a significant issue in the design of TDOA type signal location systems. Accordingly, there is an ongoing need to develop new architectures and methods for accurately locating the source of signals, while reducing the amount of data that must be communicated to a central processing station over a communication link for purposes of TDOA analysis.